Conventionally, there has been disclosed a method of acquiring a polarized image with an image pickup unit and a polarizing filter. For example, Patent Document 1 discloses a method of acquiring polarized images in a plurality of polarization directions, in the method a polarizing filter is disposed in front of an image pickup unit and shooting is performed by turning the polarizing filter. Furthermore, there has been disclosed a method of acquiring, with a polarizing filter giving any direction of a plurality of polarization directions to pixels, a polarized image in which a polarization component per polarization direction is expressed in units of pixels, by image capturing at a time.
Furthermore, there is obtained normal information regarding a subject, from a polarized image in which a polarization component per polarization direction is expressed in units of pixels. For example, in Non-Patent Documents 1 and 2, normal information is calculated with substitution of a polarization component for each of a plurality of polarization directions into a model expression.